These are also known as moss animals, sea mats, polyzoa and ectoprocts. They usually occur in colonies in the shallows, and are often mistaken for algae or sponges. Individuals are minute, usually measuring less than 0.5 mm long (see Bowerbankia sp). right. The lophophore (see diagram below left) can be retracted when the animal is disturbed. The tentacles are covered with cilia, the beating od which sets up a water current to collect food particles. These are then passed down the cilia to the mouth. There are about 4300 described species, and they have no fossil record until the Ordovician. The eggs or statoblasts of some freshwater species can withstand freezing and desiccation, and usually germinate in the spring. A freshwater bryozoan colony can be up to 5 cm long. They are usually found in clear ponds and lakes on the undersides of water-lily leaves or the upper surfaces of stones. A colony can move about 10 cm a day.